A protector module is typically provided shortly after an incoming multi-line phone cable enters into an office or apartment building, having multiple independent phone lines. The incoming multi-line phone cable includes many independent pairs of telephone wires, such as fifty pairs. The purpose of the protector module is to protect each of the independent pairs of phone lines from a power surge, such as a surge induced by a nearby lightening strike.
To accomplish this purpose, the incoming multi-line phone cable is cut, or terminated, at the protector module. Each pair of phone lines is electrically connected to one of a plurality of electrical surge protectors of the protector module. The building's internal phone lines are collectively presented to the protector module as an outgoing multi-line phone cable. The outgoing multi-line phone cable is also terminated at the protector module and has its pairs of phone lines connected to the plurality of electrical surge protectors of the protector module.
In operation, the surge protectors of the protector module respond to any power surge on one or more of the incoming phone lines by diverting the surge to the grounded chassis of the protector module. By diverting surges to ground, the surge protectors prevent the surges from passing into the phone lines of the outgoing multi-line phone cable and possibly damaging telephone equipment located within the office or apartment building.
All of the pairs of telephone wires of the incoming multi-line phone cable are surrounded by a shielding layer, which in turn is surrounded by an insulation layer. It is important to ground the shielding layer of the incoming multi-line phone cable to the grounded chassis of the protector module. Likewise, all of the pairs of telephone wires of the outgoing multi-line phone cable are surrounded by a shielding layer, which in turn is surrounded by an insulation layer, and it is important to ground this shielding layer to the grounded chassis of the protector module. By so doing, a conductive path is formed for induced currents within the shielding layers, a uniform ground is established, and electrical noise within the phone lines is reduced.
FIG. 1 is an overhead view of a protector module 1, according to the background art. An incoming multi-line phone cable 2 enters the protector module 1 through an opening provided in a sidewall 3. The incoming multi-line phone cable 2 includes numerous individual phone lines 100 (illustrated in FIG. 8) which are wire wrapped to selected individual terminals beneath a bread board 4. Each of the individual terminals beneath the bread board 4 is electrically connected to a respective electrical socket 5 provided on an upper surface of the bread board 4.
As also illustrated in FIG. 1, an outgoing multi-line phone cable 6 enters the protector module 1 through an opening provided in an opposite sidewall 7. The outgoing multi-line phone cable 6 also includes numerous individual phone lines (illustrated in FIG. 8), which are wire wrapped to different individual terminals beneath the bread board 4.
A plurality of removable and replaceable, electrical surge protectors 8 have plug terminals, which are inserted into the sockets 5 on the upper surface of the bread board 4. The electrical surge protectors 8 electrically connect the individual phone lines of the incoming multi-line phone cable 2 to the individual phone lines of the outgoing multi-line phone cable 6. The electrical surge protectors 8 include components, such as gas filled vials, which can divert a power surge from the phone lines of the incoming multi-line phone cable 2 to ground. By this arrangement, the protector module 1 can protect phone equipment, located within the office or apartment building, attached to the individual phone lines of the outgoing multi-line phone cable 6.
FIG. 2 illustrates the physical connection between the incoming multi-line phone cable 2 and the protector module 1. The physical connection between the outgoing multi-line phone cable 6 and the protector module 1 is identical to the physical connection between the incoming multi-line phone cable 2 and the protector module 1. Therefore, the later physical connection will not be described in detail.
As shown in FIG. 2, a bracket 9 is installed to a bottom of the protector module 1 adjacent the sidewall 3. The bottom of the protector module 1 includes threaded studs 10, which are passed through holes 11 formed in the bracket 9. The bracket 9 is tightly secured to the bottom of the protector module 1 by engaging washers 12 and nuts 13 to the threaded studs 10.
An upper portion of the bracket 9 includes a plurality of ribs 14. The incoming multi-line phone cable 2 is placed upon the ribs 14, and secured to the bracket 9 by a standard hose clamp 15. The hose clamp 15 presses an insulation layer 16 of the incoming multi-line phone cable 2 tightly against the ribs 14 of the bracket 9. By this arrangement, the hose clamp 15 provides strain relief to the connection by preventing any tension on the wire wrap connections between the individual phone lines and the wire wrap terminals of the bread board 4.
Inside the insulation layer 16 is a shielding layer 17. The shielding layer 17 prevents electromagnetic fields adjacent to the incoming multi-line phone cable 2 from inducing currents with the individual phone lines, and thereby prevents undesirable electrical noise. It is important that the shielding layer 17 be electrically connected to a ground potential. In order to accomplish this grounding, a clamping device 18 is provided.
The clamping device 18 includes an electrically conductive, stationary jaw 19. The stationary jaw 19 has a threaded stud 20 integrally formed therewith. A short slit is cut through the insulation layer 16 and the shielding layer 17, wide enough to accommodate the threaded stud 20. Then, the stationary jaw 19 is inserted into an end of the incoming multi-line phone cable 2 so that the stationary jaw 19 contacts the shielding layer 17, while the threaded stud 20 passes along in the slit formed in the insulation layer 16 and the shielding layer 17.
A clamping jaw 21 has a through hole 22 formed therein. The threaded stud 20 is passed through the through hole 22, and then the clamping jaw 21 is placed adjacent to the insulation layer 16. A washer 27 and nut 23 are installed on the threaded stud 20 and the nut 23 is tightened. By this arrangement, the stationary jaw 19 can be securely, electrically connected to the shielding layer 17.
A ground strap 24 connects the stationary jaw 19 to a first grounding post 25 provided on a conductive, grounded chassis of the protector module 1, adjacent the bread board 4. The outgoing multi-line phone cable 6 has its shielding sleeve connected to a second grounding post 26 provided on the grounded chassis of the protector module 1, in a manner identical to that described above in conjunction with the incoming multi-line phone cable 2. Because the grounded chassis is conductive, the first grounding post 25 is electrically connected to the second grounding post 26, and thereby the shielding sleeves of the incoming and outgoing multi-line phone cables are electrically connected.
The above described method of grounding the shielding layers of the incoming and outgoing multi-line phone cables suffers several drawbacks. The pressure exerted by the hose clamp 15, against the insulation layer 16, translates into internal stresses on the phone lines within the incoming multi-line phone cable 2. The stresses can break a conductor within a particular phone line, resulting in a loss of phone service. The stresses can deform the conductor within a particular phone line, creating a resistance in the conductor, resulting in noise in the phone service. Also, the stresses can press the phone lines closer together, resulting in cross-talk between phone lines. Further disadvantages are that a service technician must remember, and spend time installing, the clamping device 18. The clamping device 18 takes up space within the protector module 1, and the ground strap 24 presents an obstacle within the protector module 1.